Why Is Water Liquid But H2S Is Gas At Normal Temperature?


3 Answers

Faisal Scientist Profile
This is because, H20 has hydrogen bond between it's molecule (H-O-H------H-O-H) while H2S has weak Van Der Wals forces between it's molecule.Hence the molecules of H2O are strongly packed than H2S.
Katie Harry Profile
Katie Harry answered
I know one often expects that water would be a gas at room temperature because of its low molecular weight in comparison to H2S which is much heavier than it. However, it is the polarity of the water molecules that make it a liquid at room temperature. The water molecule is dipolar because of the great difference in the polarities of oxygen and hydrogen. Thus, the hydrogen bonds that develop between the molecules as a result of this make water a liquid. Similarly, the hydrogen bonds are fairly weak between hydrogen sulphide molecules (because of a smaller dipolar moment of the molecule) and so, these can not bind to each other tightly enough to be called a liquid.
thanked the writer.
Anonymous commented
The only thing wrong with the answer is the use of the word 'molecule' instead of 'atom' for O, S, H. Probably a typo that you could correct with a little edit!
Dave Cowles Profile
Dave Cowles answered
I was just going to point out the difference in MW between O and S. I didn't look up the bond strength of sulfur ATOMS and Oxygen ATOMS (not molecules) to hydrogen but it may be H-O is stronger than S-O since for one, the nuclei are further apart. Hence the overall size of H2S is larger than H2O so unless under pressure, H2S remains a gas at RT.
thanked the writer.
Anonymous commented
I was taught that the key factor is intermolecular forces due to the hydrogen bonding between water molecules, causing water to be a liquid at room temperature (as per Katie's answer). But your answer is thought-provoking too so thank you!
Dave Cowles
Dave Cowles commented
Size and steric considerations matter as well. Not sure which variables "go to Zero" as they say, quicker, and ie. Dont matter as much. My background in highly Organic so I may consider more factors than most.

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